Marine Battery Weigh in - Page 2 - SailNet Community
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post #11 of 12 Old 07-30-2009
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David...reserve capacity is not the traditional 20 hour rate that works best for boaters and inter battery comparison.
Reserve capacity is the number of minutes you can run a 25 amp load which is pretty huge for sailboats and a more useful spec for cars.

20 hour capacity is the number of amp hours a battery can deliver over 20 hours at a fixed rate. i.e. a 100 ah 20 hr rating means 5 amps for 20 hours may be withdrawn.

The two specs are NOT directly related nor can one be calculated from the other as different plate thicknesses and construction details will make some batteries perform better at the reserve capacity rate...and others at the 20 hour rate.
The reserve capacity on the Sears battery above works out to 85 amp hours at a 25amp discharge rate. I would expect it to be around 100ah-110 ah at a 20 hour rate based on size and weight but cannot say with precision.

Saurav 16 ...if the battery you linked to is the one you looks like those tabs with the warnings on them each cover 3 cell holes that need to be watered. There is no claim of a sealed battey in the description.
If what you have is truly a sealed WET cell...which are made for cars...that is a VERY bad choice for a boat on a dockside charger and I encourage you to return it and get a real fillable wet cell or a true sealed AGM.

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post #12 of 12 Old 07-31-2009
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Originally Posted by davidpm View Post
The DieHard battery above specs do not mention the amp hour capacity. I find that typical even in the deep cycle batteries. How do you compare them without that info. Can it be found anywhere else?

I found my own answer. The reserve capacity is the new supposedly better measure of battery capacity.
Right on the Sears page once you dig down, that battery specs out at 115Ah at the 20 hour rate. It actually looks like a good bang for the buck at $119

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